The Air Force’s F-35A had the highest full mission-capable rate among the three variants, but still reached only 28.5 percent in fiscal 2025. That was nearly double the rate of Marine Corps F-35Bs and Navy F-35Cs, but well below the Air Force’s 65 percent goal for the year.
For general mission-capable rates, which measure whether an aircraft can perform at least one assigned mission, Air Force F-35As reached 38.6 percent in 2025. The F-35B and F-35C variants ranged from about 54 percent to 64 percent, reversing the pattern seen in 2020 and 2021 when the Air Force led the other services in mission-capable rates.
The F-35 program office told GAO that fixing readiness problems could require $13.7 billion over the next five years. The June 11 report on F-35 sustainment said the program continues to face delayed upgrades, rising sustainment costs and newly delivered aircraft that are not yet mission capable.
Program officials told auditors that the F-35 program and U.S. services prioritized buying more aircraft early in the program’s life cycle instead of building critical depot and repair capacity. GAO said this amounted to historical underinvestment in sustainment.
As a result, the current sustainment system “cannot fully support the F-35 fleet,” the report said. Program officials warned that the sustainment structure could worsen as the fleet expands unless significant changes are made.
Douglas Birkey, Executive Director of the Mitchell Institute for Aerospace Studies, said recent missions such as Operation Epic Fury showed the aircraft’s capability when spare parts and attention are prioritized. He also noted that concentrating resources on combat operations can place additional strain on the rest of the fleet.
“The aircraft delivered in combat like none other,” Birkey said. “Those tails were properly [supplied with spare parts], supported by seasoned maintainers, and readiness was a top priority. This proves the jet can deliver when the support is aligned.”
The F-35 Joint Program Office said it agreed with GAO’s findings and supported its recommendations. Those recommendations include developing risk mitigation plans for sustainment improvement initiatives, ensuring future incentive programs improve performance and applying strict financial quality controls.
“Through our Global Support Solution Reset initiative, the JPO remains focused on achieving our 2030 readiness goals and ensuring strict fiscal accountability for every sustainment dollar spent,” the JPO said.
Lockheed Martin also commented on the report in a statement to Air & Space Forces Magazine. “Lockheed Martin continues to partner with the Joint Program Office and our industry partners to ensure we are delivering efficient and effective sustainment for the warfighter,” a company spokesperson wrote.
“We have recently invested more than $2 billion in advanced funding to accelerate spare parts to increase readiness rates across the F-35 fleet,” the spokesperson added. The Air Force operates more than 500 F-35As, most of the more than 800 F-35s in U.S. military service.
The Air Force, Navy and Marine Corps plan to buy about 1,700 more F-35s by the mid-2040s. GAO said the Air Force variant is the simplest and least expensive of the three versions.
Air Force F-35A full mission-capable rates fell from 54 percent in 2021 to 36.2 percent in fiscal 2024. They then declined further to 28.5 percent in 2025.
“Since 2020, the F-35 has not met the minimum performance goals desired by the U.S. military services by wide margins and performance has generally trended down for [full mission-capable] rates and [mission-capable] rates, particularly for the Air Force F-35A,” the GAO report said.
GAO noted that Air Force officials attributed part of the 2025 decline to acceptance of new F-35s that could not yet perform all missions because of software problems. The Technology Refresh 3 upgrade had previously led to a yearlong suspension of deliveries before an interim software release allowed deliveries to resume.
Those TR-3 aircraft were initially limited to basic training flights. According to the article, the newer jets still cannot fly in combat.
Air Force officials also told GAO that ongoing spare parts shortages and corrosion contributed to lower readiness. The Pentagon’s Global Support Solution manages F-35 sustainment by sharing spare parts among U.S. and international customers.
The F-35 supplier base has struggled to find alternative sources for canopies and other key parts. GAO also said the introduction of new configurations has added “high technical complexity” to sustainment challenges.
The Joint Program Office announced a Global Support Solution Reset last year to raise mission-capable rates to 80 percent and full mission-capable rates to 65 percent by 2030. The plan calls for more spare parts and consumables, increased investment in repairs, improved parts allocation and expanded depot repair capacity.
The reset also seeks to make the most problematic spare parts more available. It would streamline maintenance processes and staffing while adopting new maintenance tools and best practices.
GAO said the JPO needs $13.7 billion in additional funding through fiscal 2031 to address parts shortages, improve maintenance and reduce reliance on a constrained supplier base. Officials said $2.2 billion would be invested in fiscal 2026 and 2027, with half of that amount going to spare parts.
The remaining $11.5 billion would begin in fiscal 2027 and cover shortfalls in planned sustainment funding. GAO said about $7.3 billion of the total would go to depot-level spare parts and materials, $3.1 billion to expand depot capacity and $3.3 billion to maintenance and fuel.
GAO said the sustainment system should improve if those issues are addressed. It also warned that the Global Support Solution Reset may not succeed if it lacks sufficient funding.
The Air Force expects it can afford its share of the reset budget, according to GAO. The Navy and Marine Corps were less certain.
The program office acknowledged that funding remains a risk. Officials were described as optimistic that fiscal 2027 and later budgets would largely cover the required costs.
GAO said the reset plan does not address the Joint Program Office’s lack of access to critical technical data needed for the military to repair the aircraft independently. That data belongs to the contractors.
Plans are also being developed to create a working capital fund for F-35 spare parts purchasing. GAO said such a fund could allow the program to stock more parts, shorten lead times and help protect against inflation, but would not be in place before October 2028 at the earliest.
Birkey said the Air Force’s long-running underfunding of spare parts and maintenance has affected the F-35 and other aircraft programs. “I can’t emphasize how consequential underinvestment in readiness for many years was to the health of the F-35 and the entire [Air Force] aircraft inventory,” Birkey said.
“That was driven by austere budgets, which made for impossible decisions,” Birkey said. The Air Force is planning a major fiscal 2027 investment in readiness and spare parts, including $1.3 billion for “initial spares [and] depot activation/material lay-in” for the F-35.
Source: Air & Space Forces Magazine.
